It is generally known that, in order to manufacture a non-woven fabric using an airlaid process, the fibers and fibrous shreds used in the process are produced beforehand by grinding a strand-like fibrous material. Notably, natural fibers such as those made from cellulose are manufactured from this type of fibrous web. The grinding and shredding preferably takes place in what are referred to as hammer mills, where the fibrous material is fed onto the transversely aligned cutting edge of a cutting mechanism and wherein several striking elements arranged on a drum strike one end of the fibrous material projecting over the cutting edge.
A device of this type and a method of this type are, for example, already known from DE 22 45 819 A1. In the known device, the cutting edge is formed into a casing by a slotted inlet opening which encases a drum body with a plurality of striking elements. In this process, the striking elements are advanced to the inner end of the slot leaving a narrow clearance, such that the incoming fibrous material is ground by the rotating drum body. Devices of this type have the great disadvantage that very irregular fibrous shreds are produced where relatively elastic fibrous materials are used. Due to the elasticity of the fibrous material, the breaks in the fibrous material occur primarily beyond the cutting edge.
In the prior art, therefore, a method and a device are known with which the fibrous material is immobilized by an additional clamping mechanism in the region of the cutting edge. The known method and the known device are described in EP 0 386 017 B1. Here, the fibrous material is fed to the cutting edge of the cutting mechanism. A clamping mechanism is arranged at a short distance from the cutting mechanism, which features two opposing clamping jaws that grip on the lower surface and the upper surface of the fibrous material. One of the clamping jaws is designed to be moveable and this results in the fibrous material being clamped in an oscillating manner. Hence, this lends additional stability to the fibrous material during grinding.
The known method and the known device, however, have a great disadvantage insofar as the point in time at which the fibrous material is clamped and the point in time at which the fibrous material is ground must be synchronized with each other in order to obtain fibrous shreds in defined sizes. Furthermore, it is impossible with the known method and device to produce very fine fibrous shreds because of the interval as designed between the cutting mechanism and the clamping mechanism.
Thus, the object of the disclosure is to develop a generic method for grinding fibrous materials and a generic device for performing the method, such that the fibrous material can be continuously ground into very fine fibrous shreds.
A further aim of the disclosure is to produce an optimally continuous grinding process with a continuous material feed.